Lactide-based acrylate polymers

ABSTRACT

In an example, a polyacrylate is disclosed. The polyacrylate includes a ring-closed portion and a ring-opened portion. The ring-closed portion includes a set of pendant lactide groups. The ring-opened portion includes a set of pendant (O—X) groups, where X is hydrogen (H) or a non-lactide group.

I. CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application and claims priority fromU.S. patent application Ser. No. 14/606,459, entitled “LACTIDE-BASEDACRYLATE POLYMERS,” filed on Jan. 27, 2015, which is incorporated hereinin its entirety.

II. FIELD OF THE DISCLOSURE

The present disclosure relates generally to synthesis of polymers frombiobased feedstocks.

III. BACKGROUND

A class of plastics broadly known as acrylics, or polyacrylates, iscommonly used in the coatings, paints and adhesives markets, and findswidespread use as structural polymers, textiles, emulsifiers, andpackaging materials. Plastics are typically derived from a finite anddwindling supply of petrochemicals, resulting in price fluctuations andsupply chain instability. Hence, there is a need for renewable andsustainable feedstocks for synthesis of polyacrylates.

IV. SUMMARY OF THE DISCLOSURE

According to an embodiment, a process for the production of an acrylatepolymer is disclosed. The process includes reacting lactide with abromination material to form a brominated lactide. The process furtherincludes reacting the brominated lactide with an elimination material toform an acrylic monomer, and polymerizing the acrylic monomer to form anacrylate polymer.

According to another embodiment, a polyacrylate is disclosed thatincludes a ring-closed portion and a ring-opened portion. Thepolyacrylate polymer is formed by a process that includes polymerizing alactide-based acrylic monomer to form an acrylate polymer, and reactingthe acrylate polymer with a ring-opening material to form thering-opened portion. The ring-opened portion includes a first set ofpendant groups.

According to another embodiment, a polyacrylate is disclosed thatincludes a ring-closed portion and a ring-opened portion. Thering-closed portion includes a set of pendant lactide groups, and thering-opened portion includes a set of pendant O—X groups, where X ishydrogen (i.e., pendant O—H groups) or a non-lactide group.

One advantage of the present disclosure is the use of renewable andsustainable feedstocks, such as the commodity chemical lactide, forsynthesis of polyacrylates rather than the use of non-renewablepetroleum-based feedstocks. Another advantage associated with thepresent disclosure is the ability to “chemically functionalize” thelactide-based polyacrylate via a ring-opening reaction to form acrylatepolymers having a ring-closed portion (having pendant lactide groups)and a ring-opened portion (having pendant functional groups, alsoreferred to as “synthetic handles”). A further advantage associated withthe present disclosure is that the “synthetic handles” that result fromthe ring-opening reaction may be “functionalized” to form acrylatepolymers with more complex architectures.

Features and other benefits that characterize embodiments are set forthin the claims annexed hereto and forming a further part hereof. However,for a better understanding of the embodiments, and of the advantages andobjectives attained through their use, reference should be made to theDrawings and to the accompanying descriptive matter.

V. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chemical reaction diagram showing the preparation of anacrylate polymer from the cyclic ester lactide, according to oneembodiment;

FIG. 2 is a chemical reaction diagram showing a ring-opening reaction ofthe acrylate polymer of FIG. 1 to form an acrylate polymer with thecyclic diester ring either intact (a “ring-closed portion”) or opened (a“ring-opened portion”), according to one embodiment; and

FIG. 3 is a chemical reaction diagram showing functionalization of theacrylate polymer of FIG. 2 by replacing pendant functional groups in thering-opened portion of the acrylate polymer with another material,according to one embodiment.

VI. DETAILED DESCRIPTION

The present disclosure relates to synthesis of a new class of acrylicpolymers derived from the chemical lactide, which is a commoditychemical, for example derived from sugar. A high-yielding, two-stepsynthetic route from lactide forms an acrylic monomer, which ispolymerized using a radical polymerization technique to form an acrylicpolymer (also referred to herein as a polyacrylate). The lactide-basedpolyacrylate provides additional flexibility via conversion into a widearray of different acrylic derivatives with useful and tunable materialproperties under mild synthetic conditions. Thus, the polyacrylates ofthe present disclosure represent bio-based acrylates that can besynthesized from renewable resources using commodity chemicals, ratherthan non-renewable petroleum resources. Ring opening techniquesdescribed herein enable formation of irregular polymers. An irregularpolymer refers to a macromolecule that, while based on a single monomer,is not formed exclusively of a single repeating structural unit. Thus,some irregular polymers are also referred to as “pseudo copolymers.” Asused herein, the term “polymer” includes polymers formed of a singlerepeating structural unit, irregular polymers, pseudo copolymers, andcopolymers.

FIG. 1 illustrates a chemical reaction diagram 100 showing thepreparation of an acrylate polymer from the cyclic diester lactide,according to one embodiment. FIG. 1 illustrates a synthetic approach toproduce a lactide-based acrylic monomer, which may be polymerized toform a lactide-based polyacrylate. The lactide-based polyacrylate ofFIG. 1 may be useful as a “stand-alone” polymer. Alternatively, asdescribed further herein with respect to FIG. 2, a ring-opening reactionof the cyclic diester ring of the “stand-alone” polymer of FIG. 1 mayyield multiple different acrylate variations. As another example, asdescribed further herein with respect to FIG. 3, a ring-opening reactionof the cyclic diester ring of the “stand-alone” polymer of FIG. 1 mayform pendant functional groups, which may serve as “synthetic handles”for functionalization towards more complex architectures.

In the particular embodiment illustrated in FIG. 1, a lactide may beused as a starting material to prepare an acrylic monomer (referred toherein as “methylidene lactide”), which may then be polymerized to forma polyacrylate (referred to herein as “poly(methylidene lactide)”). Thelactide may have any stereo-isomeric configuration (e.g., L-, D-, Meso-)or combinations of stereo-isomeric configurations. FIG. 1 illustratesthat halogenation/dehydrohalogenation (e.g., a bromine addition andelimination reaction) may be performed on the lactide. In the example ofFIG. 1, the lactide is reacted with a bromination material (e.g.,N-bromosuccinimide (NBS)) to form a brominated lactide. As anillustrative, non-limiting example of a process of forming thebrominated lactide, lactide in benzene (e.g., 15 weight/volume percent)and NBS (e.g., 1.05 equivalents) may be stirred at 80° C., and benzoylperoxide (e.g., 0.02 equivalents in a 5 weight/volume percent benzenesolution) may be added dropwise and stirred (e.g., for 24 hours).

The brominated lactide is reacted with an elimination material (e.g.,triethylamine (NEt3)) to form the acrylic monomer. In alternativeembodiments, the bromination material and/or the elimination materialmay be different. For example, the bromination material may includebromine (Br₂) and/or the elimination material may include a differentamine or an alkoxide, among other alternatives. As an illustrative,non-limiting example of a process of forming the acrylic monomer, NEt3(1.05 equivalents in a 50 weight/volume percent solution oftetrahydrofuran (THF)) may be slowly added dropwise (e.g., 0.5 mL/min)to a solution of the brominated lactide in THF (e.g., 20 weight/volumepercent). After addition, the solution may be stirred (e.g., for onehour).

FIG. 1 illustrates that the acrylic monomer (“methylidene lactide”) maybe polymerized to form the polyacrylate (“poly(methylidene lactide)”).FIG. 1 illustrates a particular embodiment in which anazobisisobutyronitrile (AIBN) thermal polymerization method is employed.However, it will be appreciated that alternative polymerizationtechniques may be employed. For example, a different thermal initiatoror an ultraviolet (UV) initiator may be used, among other alternatives.Testing on the resulting acrylate polymer indicated an average molecularweight (M_(n)) of about 20.5 kg/mol, a dispersity (D) of about 1.82, aglass transition temperature (T_(g)) of about 231° C., and a degradationtemperature (T_(d)) of about 300° C. Size-exclusion chromatography (SEC)was done on a Waters® ACQUITY® Advanced Polymer Chromatography™ (APC)system with three 4.6 mm×150 mm APC XT columns (450 Å, 2.5 μm; 125 Å,2.5 μm; and 45 Å, 1.7 μm) connected in series and a refractive indexdetector calibrated with polystyrene standards. THF eluent was used at40° C. with a flow rate of one mL/minute. Differential Scanningcalorimetry (DSC) was done with a TA Instruments® Q100 DSC viaheat-cool-heat cycles at a heating rate of 15 K/min and a cooling rateof 10 K/min. Data from the second heating cycle is reported. Thermalgravimetric analysis (TGA) was done on a TA Instruments® Q50 TGA, andtests were performed under nitrogen gas at a heating rate of 20K/minute.

Thus, FIG. 1 illustrates an embodiment of a process for the productionof a polyacrylate from renewable resources. The lactide-basedpolyacrylate of FIG. 1 may be useful as a “stand-alone” polymer (e.g.,without further modification or reaction). Alternatively, as describedfurther herein with respect to FIG. 2, a ring-opening reaction of thecyclic diester ring of the “stand-alone” polymer of FIG. 1 (e.g., usingan alcohol, R-OH) may yield multiple different acrylate variations.Further, as described further herein with respect to FIG. 3, aring-opening reaction may form pendant functional groups (e.g., pendanthydroxyl groups in the case of a ring-opening reaction using analcohol), which may serve as “synthetic handles” for functionalizationtowards more complex architectures.

FIG. 2 is a chemical reaction diagram 200 showing a ring-openingreaction (transesterification) of the lactide-based polyacrylate of FIG.1 to form an acrylate polymer with a “ring-closed portion” (i.e., withthe cyclic diester ring intact) and a “ring-opened portion,” accordingto one embodiment. FIG. 2 illustrates that a ring-opening reaction(e.g., using an alcohol, R—OH) may be performed on the cyclic diesterring of the “stand-alone” polymer of FIG. 1 to yield a differentacrylate variation (with tailored properties). For example, using amoderate-to-long chain alcohol (e.g., butanol, 2-ethylhexanol, etc.) inthe ring-opening reaction may yield an elastomeric-type acrylate that ismore flexible than the “stand-alone” polymer of FIG. 1. As anotherexample, using a smaller and/or more rigid alcohol (e.g., methanol,benzyl alcohol, etc.) in the ring-opening reaction may yield an acrylatethat is more rigid than the “stand-alone” polymer of FIG. 1.

In the particular embodiment illustrated in FIG. 2, the polyacrylate(“poly(methylidene lactide)”) of FIG. 1 is reacted with a ring-openingmaterial (e.g., an alcohol, R—OH) in the presence of a catalyst (e.g.,triazabicyclodecene (TBD)) to form a polyacrylate having a ring-openedportion (with pendant hydroxyl groups) and a ring-closed portion (withthe lactide ring intact). The ring-opening reaction exists in anequilibrium with the initial acrylate. The distribution of reactants andproducts can be adjusted or controlled based on reaction conditions(e.g., based on Le Chatelier principles). The polyacrylate formed by thering-opening reaction may represent a polymer in which at least aportion of the lactide rings remain in a ring-closed state. In aparticular embodiment, the mole percentage of the ring-opened portion ofthe acrylate polymer is not be greater than about 95 mole percent of theacrylate polymer. FIG. 2 illustrates the ring-closed portion isrepresented as n (an integer), the ring-opened portion is represented asp (an integer), and a ring-opened molar percentage or a ring-closedmolar percentage for a particular polymer may be determined based on theintegers.

As described further with respect to the examples herein, adjusting atemperature of the ring-opening reaction may result in a change in amolar percentage of the ring-opened state relative to a molar percentageof the ring-closed state. In some cases, an increased temperature of thering-opening reaction may result in an equilibrium shift toward agreater molar percentage of the ring-opened state (e.g., more of thelactide rings may be opened). Further, the molar percentage of thering-opened portion may vary based on the particular ring-openingmaterial (e.g., alcohol) that is used in the ring-opening reaction. Asdescribed further with respect to the examples herein, for aring-opening reaction at a particular temperature, a molar percentage ofthe polymer in the ring-opened state may vary based on the particularalcohol that is selected as the ring-opening material. As anillustrative, non-limiting example, when the alcohol is methanol, amolar percentage of the polymer in the ring-opened state may be in arange between about 15 molar percent and about 81 molar percent(depending on reaction temperature). As another illustrative example,when the alcohol is n-butanol, a molar percentage of the polymer in thering-opened state may be in a range between about 15 molar percent andabout 75 molar percent (depending on reaction temperature). As a furtherexample, when the alcohol is benzyl alcohol, a molar percentage of thepolymer in the ring-opened state may be in a range between about 0 molarpercent and about 17 molar percent (depending on reaction temperature).

The following are specific, non-limiting examples of reaction conditionsand resulting products based on testing:

EXAMPLE 1 Preparation of an Acrylate Polymer Using Methanol

An acrylate polymer having a ring-opened portion and a ring-closedportion was prepared by reacting the polyacrylate (“poly(methylidenelactide)”) of FIG. 1 with methanol in the presence oftriazabicyclodecene (TBD) at about 0.1 mole percent. At a reactiontemperature of about −25° C., the resulting acrylate polymer had aring-opened mole percentage of about 15.0%, an average molecular weight(M_(n)) of about 23.6 kg/mol, and a dispersity (D) of about 2.00.

EXAMPLE 2 Preparation of an Acrylate Polymer Using Methanol

An acrylate polymer having a ring-opened portion and a ring-closedportion was prepared by reacting the polyacrylate (“poly(methylidenelactide)”) of FIG. 1 with methanol in the presence oftriazabicyclodecene (TBD) at about 0.1 mole percent. At a reactiontemperature of about 5° C., the acrylate polymer had a ring-opened molepercentage of about 34.5%, an average molecular weight (MO of about 14.6kg/mol, and a dispersity (D) of about 1.69.

EXAMPLE 3 Preparation of an Acrylate Polymer Using Methanol

An acrylate polymer having a ring-opened portion and a ring-closedportion was prepared by reacting the polyacrylate (“poly(methylidenelactide)”) of FIG. 1 with methanol in the presence oftriazabicyclodecene (TBD) at about 0.1 mole percent. At a reactiontemperature of about 23° C., the acrylate polymer had a ring-opened molepercentage of about 67.3%, an average molecular weight (MO of about 11.5kg/mol, and a dispersity (D) of about 1.43.

EXAMPLE 4 Preparation of an Acrylate Polymer Using Methanol

An acrylate polymer having a ring-opened portion and a ring-closedportion was prepared by reacting the polyacrylate (“poly(methylidenelactide)”) of FIG. 1 with methanol in the presence oftriazabicyclodecene (TBD) at about 0.1 mole percent. At a reactiontemperature of about 60° C., the acrylate polymer had a ring-opened molepercentage of about 81 percent.

EXAMPLE 5

Preparation of an Acrylate Polymer Using n-butanol

An acrylate polymer having a ring-opened portion and a ring-closedportion was prepared by reacting the polyacrylate (“poly(methylidenelactide)”) of FIG. 1 with n-butanol in the presence oftriazabicyclodecene (TBD) at about 0.1 mole percent. At a reactiontemperature of about 60° C., the acrylate polymer had a ring-opened molepercentage of about 62.3%, an average molecular weight (M_(n)) of about15.3 kg/mol, and a dispersity (D) of about 1.74.

EXAMPLE 6 Preparation of an Acrylate Polymer Using Benzyl Alcohol

An acrylate polymer having a ring-opened portion and a ring-closedportion was prepared by reacting the polyacrylate (“poly(methylidenelactide)”) of FIG. 1 with benzyl alcohol in the presence oftriazabicyclodecene (TBD) at about 0.1 mole percent. At a reactiontemperature of about 60° C., the acrylate polymer had a ring-opened molepercentage of about 16.6%, an average molecular weight (M_(n)) of about18.7 kg/mol, and a dispersity (D) of about 1.70.

Thus, FIG. 2 illustrates a ring-opening reaction (transesterification)of the lactide-based polyacrylate (“poly(methylidene lactide)”) of FIG.1 to form an acrylate polymer with a “ring-opened portion” and a“ring-closed portion” (i.e., with the cyclic diester ring intact). WhileFIG. 2 illustrates a particular embodiment of a ring-opening reactionusing an alcohol, it will be appreciated that alternative ring-openingmaterial(s) may be used. For example, the ring-opening reaction may beperformed using an amine (resulting in pendant N-H groups), ammonia, orwater, among other alternatives Further, while particular examples ofalcohols are described, it will be appreciated that alternative alcoholsmay be used in the ring-opening reaction. Illustrative, non-limitingexamples of alcohols include methanol, ethanol, propanol, n-butanol,t-butanol, s-butanol, 2-ethylhexanol, benzyl alcohol, cyclohexanol,glycidol, dodecanol, 2-ethoxyethanol, hexanol, hexadecanol, octadecanol,phenol, or 2,2,2-trifluoroethanol, among other alternatives.

FIG. 3 is a chemical reaction diagram 300 showing functionalization ofthe acrylate polymer of FIG. 2 by replacing pendant functional groups(e.g., pendant O—H groups) in the ring-opened portion of the acrylatepolymer with another material (e.g., pendant O—R′ groups), according toone embodiment. The ring-opening reaction illustrated in FIG. 2 formspendant hydroxyl (OH) groups, which may be referred to as “synthetichandles.” FIG. 3 illustrates that the pendant hydroxyl groups can bemodified to further engineer properties of the acrylate polymer. Asillustrative, non-limiting examples, the acrylate polymer may befunctionalized with a variety of alkyl halides (to form ethers),isocyanates (to form carbamates), or carboxylic acid/acid halides/esters(to form esters), among other alternatives. Different pendant groups mayimpart various properties (e.g., flexibility or rigidity) to thefunctionalized acrylate polymer.

In the particular embodiment illustrated in FIG. 3, the acrylate polymerof FIG. 2 is reacted with a functionalization material (e.g., analkyl-bromide). The functionalization material reacts with hydroxylgroups in the ring-opened portion to add different types of chemicalmoieties into the polyacrylate to further “tune” the properties of theacrylate polymer (e.g., physical properties, chemical properties,mechanical properties) for use in various applications. FIG. 3illustrates that the hydroxyl groups (O—H) in the ring-opened portion ofthe acrylate polymer of FIG. 2 are replaced by pendant O—R′ groups,where R′ may include a hydrocarbon, an organic chain with heteroatoms,or inorganic compound, among other alternatives. As in FIG. 2, thering-closed portion of the “functionalized” acrylate polymer of FIG. 3is represented by the integer n, the ring-opened portion is representedby the integer p, and a ring-opened molar percentage (with the pendantO-H groups replaced with pendant O—R′ groups) or a ring-closed molarpercentage for a particular acrylate polymer may be determined based onthe integers.

Thus, FIG. 3 illustrates that the pendant functional groups (e.g.,hydroxyl groups) formed by a ring-opening reaction of the lactide-basedpolyacrylate of FIG. 1 (“poly(methylidene lactide)”) may befunctionalized towards more complex architectures (to further engineerproperties of the acrylate polymer).

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the disclosedembodiments. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thescope of the disclosure. Thus, the present disclosure is not intended tobe limited to the embodiments shown herein but is to be accorded thewidest scope possible consistent with the principles and features asdefined by the following claims.

1. A polyacrylate comprising: a ring-closed portion that includes a setof pendant lactide groups; and a ring-opened portion that includes a setof pendant (O—X) groups, wherein X is hydrogen (H) or a non-lactidegroup.
 2. The polyacrylate of claim 1, wherein the ring-opened portionincludes pendant hydroxyl (O—H) groups, and wherein the ring-openedportion further includes a set of functional (O—R) groups associatedwith an alcohol (R—OH) that is used as a ring-opening material to formthe ring-opened portion.
 3. The polyacrylate of claim 2, wherein thering-opened portion includes a set of functional (O—R) groups associatedwith an alcohol (R—OH) that is used as a ring-opening material to formthe ring-opened portion, and wherein the ring-opened portion furtherincludes a set of functionalized (O—R′) groups.
 4. The polyacrylate ofclaim 3, wherein R′ is a hydrocarbon, an organic chain with heteroatoms,an inorganic compound, or a combination thereof.
 5. The polyacrylate ofclaim 1, wherein the ring-opened portion is not greater than about 95mole percent of the polyacrylate.
 6. A polyacrylate having a ring-closedportion and a ring-opened portion, the polyacrylate formed by a processthat includes: polymerizing a lactide-based acrylic monomer to form anacrylate polymer; and reacting the acrylate polymer with a ring-openingmaterial to form the ring-opened portion, wherein the ring-openedportion includes a first set of pendant groups.
 7. The polyacrylate ofclaim 6, wherein: the ring-opening material includes an alcohol (R—OH);and the first set of pendant groups includes pendant hydroxyl (O—H)groups.
 8. The polyacrylate of claim 7, wherein the process furtherincludes replacing the pendant hydroxyl (O—H) groups in the ring-openedportion with different pendant (O—R′) groups using a functionalizationmaterial.
 9. The polyacrylate of claim 6, wherein the process furtherincludes: reacting a lactide with a halogenation material to form ahalogenated lactide; and reacting the halogenated lactide with anelimination material to form the lactide-based acrylic monomer.
 10. Thepolyacrylate of claim 9, wherein the halogenation material includes abromination material.
 11. The polyacrylate of claim 10, wherein thebromination material includes N-bromosuccinimide.
 12. The polyacrylateof claim 9, wherein the elimination material includes triethylamine. 13.The polyacrylate of claim 9, wherein the lactide-based acrylic monomeris polymerized using an azobisisobutyronitrile (AIBN) thermalpolymerization method.
 14. A polyacrylate having a ring-closed portionand a ring-opened portion, the polyacrylate formed by a process thatincludes: reacting a lactide-based acrylate polymer with a ring-openingmaterial to form a polyacrylate having a ring-opened portion and aring-closed portion, wherein the ring-opened portion is not greater thanabout 95 mole percent of the polyacrylate.
 15. The polyacrylate of claim14, wherein the ring-opening material includes an alcohol, an amine, orwater.
 16. The polyacrylate of claim 14, wherein the ring-opened portionincludes pendant hydroxyl (O—H) groups.
 17. The polyacrylate of claim14, wherein the ring-opened portion includes a set of functional (O—R)groups associated with an alcohol (R—OH) that is used as thering-opening material.
 18. The polyacrylate of claim 14, wherein thelactide-based acrylate polymer is formed by a process that includes:reacting a lactide with a halogenation material to form a halogenatedlactide; reacting the halogenated lactide with an elimination materialto form an acrylic monomer; and polymerizing the acrylic monomer to formthe lactide-based acrylate polymer.
 19. The polyacrylate of claim 18,wherein the halogenation material includes N-bromosuccinimide, andwherein the elimination material includes triethylamine.
 20. Thepolyacrylate of claim 19, wherein the lactide-based acrylate polymer hasa number average molecular weight (M_(n)) of about 20.5 kg/mol, adispersity (D) of about 1.82, a glass transition temperature (T_(g)) ofabout 231° C., and a degradation temperature (T_(d)) of about 300° C.